OpenGL-无法显示简单的2D纹理

Question

我用glfw和glew编写了一个非常简单的OpenGL程序。它可以很好地编译并运行，但是没有显示我传递给片段着色器的简单纹理。

唯一的几何是单个四边形。

我只想显示一种纯色，即纹理的第一个元素。我知道片段着色器完全可以工作，因为我可以显示没有纹理的纯色：

#version 320 es
mediump out vec4 color;
precision mediump float;
precision mediump sampler2D;

in vec2 texCoord;
uniform sampler2D tex;

void main() {
    color = vec4(0.5, 0.75, 0.5, 1.0);
}

但是，当我使用纹理采样器时，我什么也没得到，就像采样器仅采样0（仅更改main()）一样：

void main() {
    color = vec4(texture(tex, vec2(0, 0)).rgb, 1);
}

我以我认为正确的方式填充并生成纹理（TEX_SIZE被定义为#define TEX_SIZE (32*32)）：

//Texture Data
GLfloat texData[TEX_SIZE * 3] = {1.0};

//Create texture
GLuint tex;
glGenTextures(1, &tex);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 32, 32, 0, GL_RGB, GL_FLOAT, texData);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_REPEAT);

这是整个绘制循环：

//Render loop
while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS
    && !glfwWindowShouldClose(window)) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glUseProgram(programID);

    //Texture
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, tex);
    glUniform1i(glGetUniformLocation(programID, "tex"), 0);

    //Draw the quad
    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3, GL_FLOAT, 0, gVertices);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, gIndices);
    glDisableClientState(GL_VERTEX_ARRAY);

    if (glGetError()) {
        puts((char *)glewGetErrorString(glGetError()));
    }

    glfwSwapBuffers(window);
    glfwPollEvents();
}

为什么会这样？我完全被困住了。

编辑：根据建议更改了数组初始化：

//Texture Data
GLfloat texData[TEX_SIZE * 3];
for (int i = 0; i < TEX_SIZE * 3; i++) {
    texData[i] = 1.0;
}

没有变化。输出仍然是全黑的。

Answer 1

The initial value of GL_TEXTURE_MIN_FILTER is GL_NEAREST_MIPMAP_LINEAR. But you don't generate mipmaps. This causes that the texture is not complete.

OpenGL ES 3.2 Specification; 8.17 Texture Completeness; page 205

A texture is said to be complete if all the texture images and texture parameters required to utilize the texture for texture application are consistently defined.

... a texture is complete unless any of the following conditions hold true:

• The minification filter requires a mipmap (is neither NEAREST nor LINEAR), and the texture is not mipmap complete.

Change the texture minification filter (glTexParameteri) to solve your issue:

e.g.

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);